Resting energy expenditure, adiponectin and changes in body composition of young children (EarlyBird 34)

OBJECTIVE. Serum adiponectin levels are inversely related to adiposity and resting energy expenditure (REE) in adults yet may protect against excess weight gain. Little is known of these associations in children, in whom obesity is rising. The aim of this study was therefore to investigate the relationships between REE, adiponectin and weight gain in young children. METHODS. Adiponectin by ELISA, REE by indirect calorimetry, fat-free mass (FFM) and fat mass (FM) by DEXA were measured at 6.9 years, and repeated one year later in 151 healthy children, aged 7.9±0.3 years. RESULTS. There were no significant correlations between REE and adiponectin at 6.9 years or at 7.9 years (boys r=-0.02, p=0.88 and r=0.05, p=0.69, respectively; girls r=-0.11, p=0.35 and r=0.05, p=0.70, respectively). There was no link between REE at 6.9 years and subsequent weight gain or adverse change in body composition (all r<0.20, all p>0.08). Similarly, there were no correlations between adiponectin and weight change, but there was a significant inverse association between adiponectin at 6.9 years and FFM gain in boys (r=-0.27, p=0.02). CONCLUSIONS. The relationship between adiponectin and REE has yet to appear in young children. REE is not a significant predictor of future weight gain or adverse change in body composition and, although the period of follow-up was limited, adiponectin seems unlikely to confound such a relationship in healthy young children.

Validation of foot-to-foot bioelectrical impedance analysis with dual-energy X-ray absorptiometry in the assessment of body composition in young children: the EarlyBird cohort

Foot-to-foot bioelectrical impedance analysis (BIA) is simple and non-invasive, making it particularly suitable for use in children. There is insufficient evidence of the validity of foot-to-foot BIA compared with dual-energy X-ray absorptiometry (DEXA) as the criterion method in healthy young children. Our objective was to assess the validity of foot-to-foot BIA against DEXA in a large cohort of healthy young children. Body composition was measured by foot-to-foot BIA and DEXA in 203 children (mean age 8·9 (sd0·3) years). Bland–Altman and simple linear regression analyses were used to determine agreement between methods. BIA overestimated fat-free mass by a mean of 2·4 % in boys and 5·7 % in girls, while fat mass was underestimated by 6·5 % in boys and 10·3 % in girls. The percentage fat recorded by BIA was, accordingly, also lower than by DEXA (boys 4·8 %; girls 12·8 %). In boys, however, there were correlations between the size of the difference between methods and the size of the measure under consideration such that in smaller boys fat-free mass was underestimated (r − 0·57;P < 0·001) while fat mass and percentage fat were overestimated (r0·74 for fat mass;r0·69 for percentage fat; bothP < 0·001) with the reverse in bigger boys. Mean differences between techniques were greater in the girls than in the boys but in boys only, the direction of the differences was dependent upon the size of the child. Therefore, BIA may be useful for large-scale studies but is not interchangeable with DEXA and should be interpreted with caution in individuals.

A common haplotype of the glucokinase gene alters fasting glucose and birth weight: association in six studies and population-genetics analyses

Fasting glucose is associated with future risk of type 2 diabetes and ischemic heart disease and is tightly regulated despite considerable variation in quantity, type, and timing of food intake. In pregnancy, maternal fasting glucose concentration is an important determinant of offspring birth weight. The key determinant of fasting glucose is the enzyme glucokinase (GCK). Rare mutations of GCK cause fasting hyperglycemia and alter birth weight. The extent to which common variation of GCK explains normal variation of fasting glucose and birth weight is not known. We aimed to comprehensively define the role of variation of GCK in determination of fasting glucose and birth weight, using a tagging SNP (tSNP) approach and studying 19,806 subjects from six population-based studies. Using 22 tSNPs, we showed that the variant rs1799884 is associated with fasting glucose at all ages in the normal population and exceeded genomewide levels of significance (P=10-9). rs3757840 was also highly significantly associated with fasting glucose (P=8x10-7), but haplotype analysis revealed that this is explained by linkage disequilibrium (r2=0.2) with rs1799884. A maternal A allele at rs1799884 was associated with a 32-g (95% confidence interval 11-53 g) increase in offspring birth weight (P=.002). Genetic variation influencing birth weight may have conferred a selective advantage in human populations. We performed extensive population-genetics analyses to look for evidence of recent positive natural selection on patterns of GCK variation. However, we found no strong signature of positive selection. In conclusion, a comprehensive analysis of common variation of the glucokinase gene shows that this is the first gene to be reproducibly associated with fasting glucose and fetal growth.

Little evidence for early programming of weight and insulin resistance for contemporary children: EarlyBird Diabetes Study report 19

OBJECTIVE

The aim of this study was to evaluate whether adaptive responses made to the uterine or very early infant environment are affecting the current metabolic health of young children in the United Kingdom.

METHODS

Participants were 300 healthy children and their parents from the EarlyBird Diabetes Study cohort. Children were recruited from randomly selected schools at 5 years of age. Retrospective measures were maternal prepregnancy weight (n = 230), maternal fasting glucose levels at 28 weeks of pregnancy (n = 27), birth weight, and infant weight at ages 3 and 6 weeks. Prospective measures were insulin resistance, height, weight, and percentage of body fat (sum of 5 skinfold measurements) at ages 5, 6, 7, and 8 years.

RESULTS

Maternal third-trimester fasting glucose levels were associated positively with birth weight but were not associated with either weight or insulin resistance for the same children at 8 years. Birth weight was unrelated to insulin resistance at 8 years. There were no relationships between weight change in the first weeks of life and weight, percentage of fat, or insulin resistance at 8 years. Longer breastfeeding correlated inversely, although weakly, with percentage of body fat for boys only. Current weight was correlated with insulin resistance at 8 years.

CONCLUSIONS

For these contemporary children, neither the gestational environment nor early postnatal growth predicted insulin resistance, which was best predicted by current weight. There was no evidence that predictive adaptive responses made by the fetus or infant affected the child's weight or insulin resistance later in childhood.

Does lean rather than fat mass provide the link between birth weight, BMI, and metabolic risk? EarlyBird 23

BACKGROUND

High birth weight predicts subsequent obesity, but paradoxically, a reduced risk of subsequent cardiovascular disease compared with low birth weight. This apparent paradox might be explained if high birth weight programmed a greater proportion of subsequent lean mass, which carries less cardiovascular risk than fat tissue.

AIM

The aim of this study was to test the hypothesis that the direct correlation between birth weight and subsequent body mass index (BMI) represents an association between birth weight and lean tissue, and to assess the metabolic impact of this relationship.

METHODS

A total of 234 healthy prepubertal children (133 boys, 101 girls, mean age 5.9 yr +/- 0.3 standard deviation) were studied. Birth weights were obtained from maternity records. Lean mass was measured by bioelectrical impedance. Anthropometric measures included height, weight (BMI), waist circumference, and subcutaneous fat mass (FM). Insulin resistance was assessed by the homeostasis model method. Metabolic correlates of insulin resistance included total and high-density lipoprotein cholesterol, triglycerides, and sex-hormone-binding globulin.

RESULTS

Birth weight correlated significantly with lean mass in boys (r = 0.41, p < 0.001) and girls (r = 0.27, p < 0.01). Adjusting for BMI did not improve the correlation further. After adjustment for FM, lean mass correlated inversely with triglycerides in boys only (r = -0.41, p < 0.01). Birth weight correlated inversely with triglycerides in boys (r = -0.18, p < 0.05); after adjustment for lean mass, this correlation was not significant.

INTERPRETATION

In boys, the relationships between birth weight, triglycerides, and lean mass are consistent with the hypothesis. Overall, our findings provide limited evidence in support of the argument that higher birth weight predicts lower metabolic risk because it marks programming of more lean mass.

Variation in physical activity lies with the child, not his environment: evidence for an ‘activitystat’ in young children (EarlyBird 16)

OBJECTIVE

There is currently wide interest in the physical activity of children, but little understanding of its control. Here, we use accelerometers to test the hypothesis that habitual activity in young children is centrally, rather than environmentally, regulated. By central regulation we mean a classic biological feedback loop, with a set-point individual to the child, which controls his/her activity independently of external factors.

DESIGN

Non-intervention, observational and population-based, set in the home and at school.

RESULTS

Girls were systematically less active than boys, and both weekday/weekend day and year-on-year activities were correlated (r=0.43-0.56). A fivefold variation in timetabled PE explained less than 1% of the total variation in physical activity. The activity cost of transport to school was only 2% of total activity, but over 90% of it was recovered elsewhere in the day. The weekly activity recorded by children in Plymouth was the same (to within <0.3%) as that recorded independently in Glasgow, 800 km away. Total daily activity was unrelated to time reportedly spent watching TV.

INTERPRETATION

The correlations within groups and the similarities between them suggest that physical activity in children is under central biological regulation. There are implications both for public health planners and for the potentially novel signalling pathways involved.

IOTF thresholds for overweight and obesity and their relation to metabolic risk in children (EarlyBird 20)

The International Obesity TaskForce has published paediatric cutoffs from the age of 2 years for overweight and obesity, based on adult thresholds. We question their rationale. The adult cutoffs were based on known health risk; the children's were not. Data from the EarlyBird Study show that BMI category for overweight and obesity in young children are poor markers of insulin resistance and, by implication, of metabolic risk and diabetes. Moreover, BMI is known to track poorly from early childhood to adulthood. We know even less about the tracking of insulin resistance and other indices of metabolic risk from the earliest years. Until we understand more about which children acquire such risk factors, any such thresholds for overweight and obesity should be used with caution in the very young, as they may unnecessarily stigmatise the heavier child.

Metabolic risk in early childhood: the EarlyBird Study

OBJECTIVE

For a decade or more, poor nutrition during gestation, expressed as low weight at birth, was held to be the factor responsible for insulin resistance later in life. Birth weights, however, are rising and insulin-resistant states, such as diabetes, faster still. Alternative explanations are needed for insulin resistance in contemporary society. This review cites data from the EarlyBird study on the relationships of insulin resistance and metabolic disturbance in early childhood.

DESIGN

EarlyBird is a nonintervention prospective cohort study that asks the question 'Which children develop insulin resistance, and why?' It is unique in taking serial blood samples from a young age with which to monitor the behaviour of insulin resistance and its metabolic correlates, and in its comprehensive assessment of factors known or thought to influence insulin resistance

SUBJECTS

In all, 307 randomly selected healthy school children at school entry (mean age 4.9 y) and at 12 and 24 months later.

MEASUREMENTS

In the children: Birth weight and, at each time point height, weight, body mass index (BMI, kg/m(2)), skinfolds at five sites, circumferences, resting energy expenditure, physical activity, body composition, heart rate variability, diet, HOMA-IR and HOMA-ISC, blood pressure, full blood count, haemoglobin and haematocrit, HbA1C, total cholesterol, HDL cholesterol, LDL cholesterol, triglycerides, uric acid, IGF-1, gonadotrophins and SHBG. In their parents: At baseline height, weight, BMI, waist circumference, HOMA-IR and HOMA-ISC, full blood count, haematocrit, HbA1C, total cholesterol, HDL cholesterol, calculated LDL cholesterol, triglycerides, uric acid, gonadotrophins and SHBG.

RESULTS

Four observations are reported here: (1) There are clear correlations in contemporary children between insulin resistance and weight at 5 y, but none with birth weight. (2) Females throughout life are intrinsically more insulin resistant than males. (3) The substantial variation of physical activity among young children is attributable to the child, and not to his environment. (4) There is dissociation in young children between fatness and insulin resistance.

CONCLUSION

There is much yet to be learned about the development of obesity and insulin resistance in children. The notions of overnutrition and underactivity alone are too simplistic.

The impact of pregnancy weight and glucose on the metabolic health of mother and child in the south west of the UK

OBJECTIVE

to explore relationships between maternal pre-pregnancy weight, third trimester glucose, baby birth weight, weight and metabolic health of the mother and child 5 years after birth.

DESIGN

an observational study set within a non-intervention, longitudinal cohort study looking at insulin resistance in children.

SETTING

a teaching hospital in the south west of the United Kingdom.

PARTICIPANTS

300 mothers and their five-year-old children from randomly selected Plymouth schools, stratified according to socioeconomic status.

MEASUREMENTS

were obtained from obstetric records maternal pre-pregnant weight, random and fasting third trimester blood glucose, baby birth weight. Five years later the following measurements were made of the mother and child: height, weight, glucose and insulin resistance.

FINDINGS

five years after the pregnancy, 33% of the mothers were overweight, with an additional 19% obese. In the children 13% of boys were overweight (4% obese), and in the girls, 26% were overweight (5% obese). In the five-year-old children, weight (r=0.28, p<0.001) but not birth weight (r=0.03, p=0.573), correlated with insulin resistance. Maternal pre-pregnant weight was related to both random and fasting third trimester glucose, and to insulin resistance 5 years later. Third trimester fasting glucose, even within a normal range, was a better predictor than random glucose of the baby's birth weight (r=0.39, p=0.044) and the mother's future insulin resistance (r=0.67, p<0.001). No maternal measures predicted insulin resistance in the child at 5 years.

CONCLUSIONS

maternal weight had an important influence on the gestational environment, and predicted insulin resistance 5 years later. Fasting glucose, even within the reference range, was a better predictor than random glucose of the baby's birth weight and the mother's future insulin resistance.

IMPLICATIONS FOR PRACTICE

these concern the importance of pre-conception weight management, and support replacement of routine random glucose sampling during the third trimester with an earlier, fasting measurement.

The psychological burden of short stature: evidence against

Short stature, per se, is clearly not a disease, but is commonly perceived to be associated with social and psychological disadvantage. The assumption, widely held by pediatricians that short children are likely to be significantly affected by their stature, has been founded largely on older, poorly designed clinic-based studies and laboratory investigations of beliefs about the association between stature and individual characteristics. In contrast, data from more recent and better designed clinic- and community-based studies show that, in terms of psychosocial functioning, individuals with short stature are largely indistinguishable from their peers, whether in childhood, adolescence or adulthood. Parents and children alike should be reassured by these findings. In the absence of clear pathology, physical or psychological, GH therapy for the short but otherwise normal child raises ethical concerns about so-called 'cosmetic endocrinology'.

Sex differences in resting energy expenditure and their relation to insulin resistance in children (EarlyBird 13)

BACKGROUND

Insulin resistance is believed to be the process underlying type 2 diabetes and premature cardiovascular disease. We have established that a relation between body mass and insulin resistance calculated by homeostasis model assessment (HOMA-IR) exists by 5 y of age in contemporary UK children. Resting energy expenditure (REE) is variable among individuals and is one of many factors controlling body mass.

OBJECTIVE

The objective was to investigate the relations between REE, body mass, and HOMA-IR in young children.

DESIGN

EarlyBird is a nonintervention prospective cohort study of 307 healthy 5-y-olds that asks the question: Which children develop insulin resistance and why? REE by indirect calorimetry and HOMA-IR were measured in addition to total body mass, fat-free mass (FFM) by bioimpedance, body mass index (BMI; in kg/m(2)), and skinfold thickness when the mean age of the cohort was 5.9 +/- 0.2 y.

RESULTS

Whereas the BMI of the boys was lower than that of the girls (x +/- SD: boys, 15.9 +/- 1.9; girls, 16.5 +/- 1.9; P = 0.03), their REE was higher by 6% (x +/- SD: 4724 +/- 615 compared with 4469 +/- 531 kJ/d; P = 0.002). This difference persisted after adjustment for FFM and other anthropometric variables (P = 0.04). In boys, there was a weak, although significant, inverse correlation between REE and HOMA-IR, independent of fat mass and FFM (boys: r = -0.21, P = 0.03; girls: r = 0.12, P = 0.34).

CONCLUSION

There is a sex difference in REE at 6 y of age that cannot be explained by body composition. The difference appears to be intrinsic, and its contribution to sex differences in adiposity and HOMA-IR in children merits further exploration.

Lack of support for a role of the insulin gene variable number of tandem repeats minisatellite (INS-VNTR) locus in fetal growth or type 2 diabetes-related intermediate traits in United Kingdom populations

The insulin gene variable number of tandem repeats minisatellite (INS-VNTR) class III allele is associated with altered fetal growth, type 2 diabetes risk (especially when paternally inherited), and insulin and IGF2 gene expression. Further studies are needed to establish the role of the INS-VNTR in fetal growth and assess whether its effects depend on the parent of origin. We analyzed the INS-VNTR-linked -23 Hph1 polymorphism in 2283 subjects, comprising 1184 children and 1099 parents. There were no differences (P < 0.05) in birth weight between offspring of the three genotypes: III/III (n = 108) vs. I/I (n = 558), effect size, -8 g (P = 0.87); and I/III (n = 464) vs. I/I, effect size, -19 g (P = 0.54). We observed no differences in head circumference [III/III (n = 95) vs. I/I (n = 470), effect size, -0.14 cm; P = 0.31] or birth length. No differences were observed when stratifying by postnatal growth realignments [nonchangers III/III (n = 37) vs. I/I (n = 170), effect size, -43 g; P = 1.00] or by parent of origin of the class III allele (presence of paternal III allele effect size, -15 g; P = 0.74). INS-VNTR was nominally associated (P < 0.05) with body mass index and insulin resistance, but not with beta-cell function, in young adults. In the largest study to date, we found a lack of support for a role for INS-VNTR in fetal growth and nominal association with type 2 diabetes-related intermediate traits.

Girls at five are intrinsically more insulin resistant than boys: The Programming Hypotheses Revisited--The EarlyBird Study (EarlyBird 6)

OBJECTIVE

Recent studies of type 2 diabetes in young populations consistently show a predominance of affected girls over boys. Girls are more insulin resistant than boys. We aimed in the present report to establish how much of the sex difference in insulin resistance is intrinsic.

METHODS

EarlyBird is a community-based, nonintervention cohort study of 307 healthy children from school entry at age 5 years. It asks the question: which children are insulin resistant and why? Anthropometric measures, physical activity, resting energy expenditure, and insulin resistance and its metabolic correlates were measured.

RESULTS

At 5 years, insulin resistance was 35% higher in girls than in boys. Girls carried 26% more subcutaneous fat despite similar body weights. However, after correcting for anthropometric variables and physical activity, girls remained 33% more insulin resistant than boys. Triglycerides were significantly higher in girls, and high-density lipoprotein cholesterol and sex hormone-binding globulin were significantly lower.

CONCLUSIONS

Sex-linked genes may account for the intrinsic sex difference observed. These genes may have an important impact on the development of insulin resistance and the metabolic syndrome and may help to explain the female preponderance of type 2 diabetes in children. Their identification may also help in understanding the pathogenesis of insulin resistance.

Preventable factors in childhood that lead to insulin resistance, diabetes mellitus and the metabolic syndrome: the EarlyBird diabetes study 1

For a decade or more, poor nutrition during gestation, expressed as low weight at birth, was held to be the factor responsible for insulin resistance later in life. Birth weights, however, are rising and insulin resistant states, such as diabetes mellitus, faster still. Alternative explanations are needed to explain insulin resistance in contemporary industrialised populations. EarlyBird is a non-intervention prospective cohort study that asks the question 'Which children develop insulin resistance, and why?' It is unique in taking serial blood samples from a young age with which to monitor the behaviour of insulin resistance and its metabolic correlates. This, the baseline report of the EarlyBird Study, describes the rationale, design and methodology of the study, and the profile of the population at entry. It situates the anthropometric, physical activity and dietary status of the EarlyBird children and provides a detailed metabolic profile of the British 5 year-old in the year 2000.

The relative contributions of birth weight, weight change, and current weight to insulin resistance in contemporary 5-year-olds: the EarlyBird Study

For more than a decade, the fetal programming hypothesis has taught that insulin resistance and its associated metabolic disturbances result from poor gestational environment, for which low birth weight is a surrogate. Low birth weight, however, is now uncommon in industrialized societies. We have investigated the relevance of birth weight, "catch-up" weight, and current weight to insulin resistance in 300 contemporary British children. Insulin resistance at 5 years was not related to birth weight but was correlated with current weight and weight catch-up in both sexes, more strongly so in girls (r = 0.33, P < 0.001 vs. r = 0.18, P = 0.03), who were intrinsically more insulin-resistant than boys. Weight change merely co-correlated with current weight (r = 0.67, P < 0.01 in both sexes) and did not improve on the prediction of insulin resistance. Most important, insulin resistance at 5 years was the same in children of heavier birth weight, whose weight SD score had not changed, as in those of lighter birth weight, matched for current weight, who had experienced so-called catch-up (boys 0.89 and 0.88 units, respectively, P = 0.96; girls 1.26 and 1.13 units, P = 0.41). Insulin resistance in contemporary children seems to be a function of excess current weight rather than of low birth weight or change in weight.

Technical reliability of the CSA activity monitor: The EarlyBird Study

PURPOSE

To evaluate the technical performance of the CSA accelerometer-based activity monitor.

METHODS

Twenty-three CSA monitors were subjected to intra- and inter-instrument variability tests by controlled trials using a motorized turntable. The CSA monitor measures change in acceleration, and precision was tested by producing sinusoidal variations in speed around two fixed baseline speeds (fast and medium). The angle of the monitor to the line of force along the radius of the turntable was varied using tilted blocks. Three sets of tests were carried out. 1. Intra-instrument variability: seven monitors were tested three times in each of the four quadrants. 2. All 23 monitors were used for inter-instrument tests. 3. The effects of tilt at 15 degrees, 30 degrees, and 45 degrees were carried out on six monitors.

RESULTS

Intra-instrument coefficients of variation (CV) never exceeded 2% for fast or medium speed and achieved "between run" intra-class correlation coefficients (ICC) of 0.92 and 0.84 respectively. There were no significant differences between the monitors in terms of repeatability (fast: = 0.97, medium: = 0.77). Although there were significant differences between monitors in terms of mean score, inter-instrument variability did not exceed 5% at either speed. Inter-batch ICCs ranged from 0.87 to 0.98 for fast and from 0.71 to 0.99 for medium. The angle test results corresponded closely to those predicted theoretically, with a loss in mean score of only 6% when the monitor was tilted from 0 degrees to 15 degrees.

CONCLUSION

The CSA monitor provides a precise tool for measuring changes in acceleration in laboratory settings. Technically, the device performs well, and is likely to prove a useful tool in the assessment of physical activity in children and adults.

The psychosocial consequences of short stature: a review of the evidence

The advent of biosynthetic growth hormone (GH) has been accompanied by a transformation in the clinical management of youths with short stature. An important--if not always explicitly stated--goal of endocrine therapies is an improvement in the psychological adaptation of individuals with short stature. Negative stereotypes regarding short stature constitute a potential source of psychosocial stress for the affected child and, in turn, the entire family. Nevertheless, studies have demonstrated that the psychological adaptation of individuals who are shorter than average is largely indistinguishable from others, whether in childhood, adolescence or adulthood. "Short stature" as an isolated physical characteristic appears to hold little value as a predictor of the individual's psychological adaptation or quality of life. In order to avoid the unwarranted medicalizing of healthy short stature, clinicians would be well advised to incorporate factors beyond auxology in the decision-making algorithm when selecting and preparing patients for possible growth-promoting therapies.

Accelerometers identify inactive and potentially obese children (EarlyBird 3)

Accelerometers revealed a fivefold variation in physical activity among healthy 5 year old children. They singled out habitually inactive children, most of them girls, who did little, whether at school or over the weekend. Accelerometers are of potential value in identifying, from an early age, children at risk of becoming obese.